Set ENV.deparallelize in httrack formula.

The build was failing at link time when attempting parallel
make. Setting ENV.deparallelize builds httrack successfully.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>

Formula/httrack.rb

@@ -7,6 +7,7 @@ class Httrack <Formula
   version '3.43-9C'
 
   def install
+    ENV.deparallelize
     system "./configure", "--disable-debug", "--disable-dependency-tracking",
                           "--prefix=#{prefix}",
                           "--enable-shared=no"